Linking lights to single parameter in Cycles
OK, so my options now are:
1) place the lights on a separate layer and set their intensities then use the filmic response options to determine 'exposure'. As long as the lights are accurately calibrated to all lights in the scene, this will work.
2) master parameter drivers as Jerryno indicated above. Probably the most technically correct option.
3) Set a master light first, apply any textures, then use alt D to make copies. These take their data from the original light. I just tested it and it works just fine. Make sure to name the light before making copies if using multiple lighting sets.